Quality bags generally have a leather skin while general, wide-spread bags have a synthetic leather skin.
Some synthetic leather skins are made of vinyl chloride, which may produce toxic gases during waste treatment.
Polyurethane materials have been extensively used in synthetic leather bags in the prior art because they provide a texture similar to that of leather. Such polyurethane materials are used to coat the surface of a base fabric to form the skin.
However, when bags having a polyurethane skin become wet by rain or are stained with a user's sweating hands, the moisture and polyurethane may be subject to hydrolysis, deteriorating the material. Consequently, for example, the skin surface likely cracks and peels off at the handles after extended use.
Colored parts may fade or the skin surface may turn yellow under the sun or fluorescent lighting.
According to these viewpoints, the composition of synthetic leather has been attempted using polycarbonate, which has excellent hydrolysis resistance.
In Japanese Patent No. 3281126, in order to form synthetic leather where the hydrolysis resistance can be improved in no-yellow discoloration type polyurethane, technologies for synthetic leather and artificial leather using polyurethane, which has been obtained using polytetramethylene carbonate diol, are disclosed.
However, in these technologies described in the above Patent Literature, in general, a technology consisting of a coating agent composition using polycarbonate from the viewpoint to improve the hydrolysis resistance is merely disclosed, and no specific technical composition in the case of forming the skin material of bags is mentioned at all.
The purpose of the present invention is to provide a bag having excellent water and perspiration resistance, the skin of which shows no deterioration after extended use, has light resistance and experiences no discoloration or yellowing under the sun or fluorescent lighting.
Moreover, an object of the present invention is to provide a bag that does not experience deformation or loss of shape during use, even when stress is applied to the skin material due to the weight of its contents after extended use. In addition, another object is to provide a bag where a surface of the skin material is smooth and the quality of apparent condition is excellent.